In chain saws driven by two-stroke engines, the exhaust gases discharged from the cylinder reach the muffler with a temperature of approximately 600.degree. C. Through the chemical conversion process in the catalyzer wherein hydrocarbons are converted to carbon dioxide and water, the temperature can increase to approximately 1,000.degree. C. because this conversion process is exothermal. The scavenging losses which are typical for a two-stroke engine cause energy-rich exhaust gases to be available for the conversion process so that during this conversion process heat energy is released which corresponds approximately to the energy delivered by the engine.
In practice, it has been shown that an ignition of the treated exhaust gases can occur because of the energy-rich exhaust gases typical for the two-stroke engine and because of the temperature increase brought about by the conversion process.